The invention relates to a planet carrier for a gearbox, especially an automatic gearbox or a powershift gearbox, in which planet gears are mounted on pins and these planet gears engage a sun gear, which is arranged coaxial to the center axis of the planet gear, and an internal geared wheel. Furthermore, the planet carrier is provided with a plate body for clutch or brake plates.
Planetary gearboxes of the above-noted type are used primarily in automatic transmissions or powershift gearboxes. They comprise a central sun gear, an internal geared wheel arranged concentric to the sun gear, and several planet gears, which are arranged between the sun and the internal geared wheel. The rotational axes of the planet gears are aligned parallel but with axial spacing to the axes of the sun gear and the internal geared wheel, with the teeth of the planet gears being in constant engagement with the teeth of the sun gear or the internal geared wheel. The planet gears are mounted rotatably on a planet carrier. The planet carrier, sun gear, and internal geared wheel can be coupled to each other or to a stationary gearbox component for changing the gear transmission ratio, whereby the components coupled to each other are held to the same rpm or fixed so that they cannot rotate. The coupling of various components is generally implemented through brake or plate clutches.
Planet carriers for gearboxes are known, which comprise a one-piece or multiple-piece carrier flange for the planet gears and a rotationally symmetric cup-shaped part. Teeth for clutch plates or brake plates are typically formed on the cup-shaped part. Such a device is known from DE 195 44 197. Accordingly, the planet carrier is constructed from a support base and a support cover, which define two parallel, spaced support planes separated by spacer columns. The connection between the support base and the support cover is produced by means of a weld connection via radially outwardly pointing flange plates formed on the open ends of the spacer columns. In this way, the flange plates are connected to each other by means of ring segments. It is further explained that the support base is to be produced as a cast or forged part, which leads to the fact that expensive finishing work must be performed on the support base in the region of the spacer columns. Additional disadvantages of this solution are high production costs of cast or forged parts, their high weight, and low strength in the region of edges.
Another configuration of a planet carrier is shown in German Patent Publication DE 43 02 844. Here, the configuration involves a planet carrier comprising a planet carrier hub part and a side wall component, which are formed as extruded or sheet-pressed parts. The side wall component is a cup-shaped plate body, while the planet carrier hub part comprises a ring-shaped disk and a tubular projection. Both components are rotationally symmetric with the exception of impressions, which extend in the axial direction. The impressions extend from the base of the side wall component outwards in the axial direction and from the disk of the planet carrier hub part axially away from the ring-shaped projection. The shape of the axial impressions makes complicated processing steps necessary during the shaping process.
When the planet carrier is assembled, the two components are welded to each other in the region of the impressions. Here, it must be guaranteed that they are positioned exactly both in the axial and also in the radial and peripheral directions. This requires enormous accuracy in the formation of the impressions and complicated positioning and centering means in the production of the weld connection, which counteracts an economical production of the planet carrier.